The present inventions relate generally to electric motors, and more particularly, to a motor with reduced torque ripple.
One type of electric motor is known as a synchronous reluctance motor. In a synchronous electric motor, the rotor rotates at a speed that is synchronized with the frequency of an AC power source (i.e., the field rotation of the stator). Induction motors, by contrast, are asynchronous since the rotor rotates at a slower speed than the stator field. A synchronous reluctance motor has pole regions of high magnetic permeance and insulated regions of low magnetic permeance. As the stator field rotates, the pole regions of the rotor are attracted by the stator field in order to rotate the rotor. A synchronous permanent magnet motor includes magnets in the rotor that are attracted to and/or repelled by the stator field to cause the rotor to rotate.
Torque ripple occurs in electrical motors when the design of the motor results in torque variations as the rotor makes a single revolution. Torque ripple may be caused by various factors related to the design of a motor. In general, torque ripple is produced by the changing alignment and misalignment of the stator and rotor as the rotor rotates through one revolution. A large variation in torque output as the motor rotates (i.e., torque ripple) is undesirable because it results in vibration and noise among other problems. Thus, electrical motors with low torque ripple are desirable.